1. Field of the Invention
This invention relates generally to the field of communication systems, and more particularly to an integrated paging and radiotelephone system providing improved paging reliability.
2. Description of the Prior Art
Paging systems and radiotelephone systems, such as cellular radiotelephone systems have gained widespread acceptance over the years. The trend in growth of these systems has continued to be positive, especially as the technology has evolved to enable reductions in the size and weight of the pagers and portable cellular telephones. Many of the users of portable cellular telephones have continued to be users of pagers, which has resulted in the requirement that those users carry not only a portable cellular telephone, but also a pager. With the trend in technology continuing to enable further miniaturization of both portable cellular telephones and pagers, it is now possible to combine both elements into a single portable unit. Such a combination, however, has been shown to create potential problems not previously encountered when both the portable cellular telephone and the pager were separate units. The close proximity which exists between the paging receiver and the cellular telephone transmitter when the units are combined into a single unit, has been shown to result in significant desensitization of some paging receivers when the portable cellular radiotelephone is in use. The level of the desensitization problem has been shown to be, at least in part, a function of the operating frequency of the paging receiver. As a result receiver desensitization has been found to be especially significant when the pagers are assigned to the 900 MHz frequency band which is close to the cellular transmitter transmit frequencies, and to a lesser extent at other paging frequencies. Such desensitization can result in the loss of pages, when those pages are transmitted during the time a telephone conversation is in progress using the portable cellular telephone. There is, as a result, a need to improve the reliability of the paging transmissions for those pagers which are combined into a single unit with a portable cellular telephone.